I have a home that was made in 1978 and it is cold inside. I am trying to figure out how much fiberglass insulation I am going to need for a home that is 1232 sq ft. Don't want to spend more than I have to on a tight budget.
Measure your attic space.
Look at the insulation package to find out how many square feet it covers.
Divide your total square footage by that number, and you get the number of insulation packages you need. For a fraction, round up.
Now, multiply that number by the price for each package, add the tax - and there is your total material cost, not including protection attire.
Too difficult? hire an installer.
In addition, there are other ways to make the house more efficient. Some of them are very inexpensive, like weatherstripping. Some are more involved, like new windows.
YouTube has a number of helpful videos.
A house built in 1978 should have a minimum of R-19 in the attic already and R-11 in the walls. A lot of houses built in that timeframe had R-30 in the attic. You need to see what is up there now. If you already have R-30, adding more will not help you much, not that you would be able to measure.
The insulation in the attic should cover the tops of the ceiling joists. Exposed joists act like a heat sink. If you have a truss roof, then even R-19 will cover the joists. If you have a conventional ceiling with 2x6 or 2x8 joists, then you would need more insulation.
If your house is on a slab, it can feel really cold. If the edges of the slab are exposed, the are often coated with a stucco or some other coating. Remove the coating, glue 1/2 rigid foam board to the slab and then skim coat or stucco over the foam. Also pull up your base boards, or at least the final quarter round that covers the edges of the carpet and caulk the sill plate to the slab to insure no cold air blows under there. You would be amazed at how much cold air comes in that way.
If you have an R-30 in the attic, then your windows could easily account for more heat loss than the attic. Aluminum framed, single hung, single pane with storms were very common at that time. There was also probably no insulation stuffed between the window frame and the opening for the window. Unfortunately that means pulling out a lot of sheetrock just to add a few square inches of insulation, probably not worth the effort.
One trick I did in this situation that was pretty cheap and really helped was to make an interior frame that just fit inside the wall opening for the window. I made it out of 1x1, covered it on both sides with an ultra clear vinyl and put weatherstripping around the edges and press fitted it into each window opening for the window. Storing all these for the summer was the only downside. They easily paid for themselves in one season, probably in the first month.
Check all your window and door weatherstripping, this usually gives you the biggest return on investment in terms of time and money.